Attribute-Based On-Demand Multicast Group Setup with Membership Anonymity

In many applications, it is desired to dynamically establish temporary multicast groups for secure message delivery. It is also often the case that the group membership information itself is sensitive and needs to be well protected. However, existing solutions either fail to address the issue of membership anonymity or do not scale well for dynamically established groups. In this paper, we propose a highly scalable solution for dynamical multicast group setup and yet protecting group membership anonymity simultaneously. In the proposed solution, scalability and membership anonymity are achieved via a novel design that integrates both ciphertext-policy attribute-based encryption (CP-ABE) and centralized flat table (CFT) techniques. In our design, multicast groups are specified through group member attributes represented through binary member ID only and thus achieves scalability. Also, high level of membership anonymity is guaranteed such that every group member knows nothing but his own group membership only. The proposed solution is also efficient in communication, that is, the ciphertext size is only O(n), where n is the length of a group member ID and independent to the group size.